This invention relates to the drying of tobacco products such as cut rag, cut rolled stem and homogenised leaf.
The main object in the drying of tobacco products is to achieve a fixed moisture content with a very small standard deviation.
It has already been proposed to avoid variations in the control of the drying process, by premoistening the products to a constant moisture content before they enter the drying stage. In this proposal incoming tobacco is moistened by a combination of steam and water sprays to a constant moisture content. When this method was employed the quality of the tobacco improved, but there still was an unaccountable variation in the physical characteristics of the product.
The present invention is based on the discovery that the variation referred to above can be attributed to the variation in temperature in the drying stage.
In U.S. Pat. No. 3,905,123 it has already been proposed to compute the dry tobacco mass flow rate and to measure the temperature of the product. This information is used to control the drier. The present invention uses the same information, but makes use of it in a different manner.